1. Field of the Invention
The present invention relates to an expansion unit for expanding the functions of a computer system and a computer that can be connected to the expansion unit.
2. Description of the Related Art
Various personal portable computers of lap-top and notebook type easy to carry and operable with a battery have recently been developed. The portable computers of these types are so configured that an expansion unit can be mounted on them as required for expanding the functions thereof.
The expansion units include a drive bay for accommodating a drive unit such as a hard disk drive and an expansion slot for mounting various option cards. The expansion units, when used by being connected with a portable computer as required, facilitate the expansion of the functions of the portable computer without adversely affecting the portability of the portable computer.
The conventional expansion units, however, lack the security for mounting and dismounting a personal computer. In the prior art, for example, a portable computer connected with an expansion unit can be easily removed by anyone. The portable computer (the computer main body) connected with the expansion unit, therefore, is liable to be removed and carried away. Also, a conventional expansion unit can be used by anyone who owns a portable computer connectable to the expansion unit. As a result, the option card in the expansion unit is exposed to the danger of being misused without permission or the data stored in the hard disk is sometimes illegally read out or otherwise damaged by a mischievous conduct of a third party.
In recent years, an operating system or a basic input-output system (BIOS) having the function of automatically restructuring the system environment like the plug-and-play (PnP) has been under development. Utilizing this operating system or the BIOS, the system environment can be automatically changed to the one usable for an option card or the like. The recent trend, therefore, is toward an easier illegal use of an expansion unit by a third party.
The recent years has also seen the development of a simple-type expansion unit such as a port replicator with a PC card controller built therein. The same portable computer, therefore, can be selectively connected to a plurality of expansion units to suit a particular application. If the above-mentioned plug-and-play convenience is to be realized effectively in this application environment, the function is required of recognizing the type of expansion unit connected as well as the connection or disconnection of an expansion unit. This function has not conventionally been realized.